Berberine sulfate: antimicrobial activity, bioassay, and mode of action

Berberine sulfate was shown to possess antimicrobial activity against a wide variety of microorganisms including Gram-positive and Gram-negative bacteria, fungi, and protozoa. The antibacterial activity against Vibrio cholerae and Staphylococcus aureus was dependent on the inoculum size of the test organism and pH of the medium. A method of microbiological assay sensitive to 5–10 μg/ml of the drug was developed. The drug was shown to exert a more rapid antibacterial activity than chloramphenicol and tetracycline on V. cholerae, the K values being 2.4 ×10⁻² sec⁻¹, 7.8 × 10⁻³ sec⁻¹, and 5.2 × 10⁻³ sec⁻¹ respectively. Berberine sulfate was shown to be bacteriocidal to V. cholerae and bacteriostatic to S. aureus, at concentrations of 35 and 50 μg/ml. In both these organisms concentrations of 35 and 50 μg/ml of the drug inhibited ribonucleic acid (RNA) and protein synthesis almost immediately after the addition of the drug. There was little effect on deoxyribonucleic acid (DNA) synthesis at these concentrations.